With the advent of smaller and smaller cellular telephones, it has become increasingly necessary to provide means for shielding the user and various electrical components of the telephone from radio-frequency (RF) emissions from other components of the telephone and/or from the environment. Electrically conductive shield cans may be mounted on a printed circuit board (PCB) and shaped to surround the components which are to be protected from RF noise or, more commonly, to suppress RF noise from the components contained in the shield cans. Shield cans according to the prior art may suffer from a number of drawbacks. The shield cans may be costly to install. Typically, shield cans are manually soldered, a labor intensive process, or mounted on a PCB during the surface mount assembly (SMA) process.
A liquid crystal display (LCD) assembly may be mechanically fastened to the inside of a front cover of a telephone or attached to one or more edges of a PCB. A light guide and associated fastening means often require a large amount of space on the PCB. The assembly process for mounting the light guide and the LCD on the PCB may be costly and labor intensive as well.
The LCD electrical connections to the PCB may be made using elastomer or spring connectors. This arrangement may be unreliable. Elastomer connectors may be improperly installed, resulting in failed electrical connections or shorting of adjacent pads on the PCB. The elastomer connectors may leave the LCD pads on the PCB vulnerable to contamination, particularly when the LCD-elastomer interface is subjected to temperature and humidity stresses over time.
If repairs of the PCB are required, the entire shield can often must be removed. This often requires expensive shield can removal equipment, fixtures and trained technicians. Typically, the PCB and surrounding components are placed under additional heat stress during both the removal and replacement of the shield can. There is also risk of flux and solder contamination of critical areas on the PCB such as LCD, SIM, or battery pads. If the board is not successfully repaired or if components reflow and shift during the re-application of the shield can, the process typically must be repeated. Snap-on shield cans are known, but are typically expensive and add additional labor to the assembly process.